The story goes that Newell was doing analytics for Microsoft by running software that scanned and reported what people had installed on their PCs -- this was back in the Windows 3.x days when Microsoft sought consent from the user before doing this kind of thing. Microsoft wanted to know how many PCs had Windows running on them. Gabe's market research found that a great many PCs did have Windows -- Windows was the second most installed software on the PCs surveyed.
Number one was Doom.
After that, Gaben started thinking maybe gaming was a better play.